#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<assert.h>
#include<unistd.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/wait.h>

#define LEFT "["
#define RIGHT "]"
#define LABLE "#"
#define DELIM " \t"
#define LINE_SIZE 1024
#define ARGC_SIZE 32
#define EXIT_CODE 44

int lastcode = 0;
int quit = 0;
extern char **environ;
char commandline[LINE_SIZE];
char *argv[ARGC_SIZE];
char pwd[LINE_SIZE];

char myenv[LINE_SIZE];

const char *getusername()
{
    return getenv("USER");  
}

const char *gethostname()
{
    return getenv("HOSTNAME");
}

void getpwd()
{
    getcwd(pwd, sizeof(pwd));
}

void interact(char *cline, int size)
{
    getpwd();
    printf(LEFT"%s@%s %s"RIGHT""LABLE" ", getusername(), gethostname(), pwd);
    char *s = fgets(cline, size, stdin);
    assert(s);
    (void)s;
    cline[strlen(cline) - 1] = '\0';
}


int splitstring(char cline[], char *_argv[])
{
    int i = 0;
    argv[i++] = strtok(cline, DELIM);
    while(_argv[i++] = strtok(NULL, DELIM));
    return i - 1;
}

void NormalExcute(char *_argv[])
{
    pid_t id = fork();
    if(id < 0)
    {
        perror("fork");
        return ;
    }
    else if(id == 0)
    {
        execvp(_argv[0], _argv);
        exit(EXIT_CODE);
    }
    else 
    {
        int status = 0;
        pid_t rid = waitpid(id, &status, 0);
        if(rid == id)
        {
            lastcode = WEXITSTATUS(status);
        }
    }
}

int buildCommand(char *_argv[], int _argc)
{
    if(_argc == 2 && strcmp(_argv[0], "cd") == 0)
    {
        chdir(argv[1]);
        getpwd();
        sprintf(getenv("PWD"), "%s", pwd);
        return 1;

    }
    else if(_argc == 2 && strcmp(_argv[0], "export") == 0)
    {
        strcpy(myenv, _argv[1]);
        putenv(myenv);
        return 1;
    }
    else if(_argc == 2 && strcmp(_argv[0], "echo") == 0)
    {
        if(strcmp(_argv[1], "$?") == 0)
        {
            printf("%d\n", lastcode);
            lastcode = 0;
        }
        else if(*_argv[1] == '$')
        {
            char *val = getenv(_argv[1] + 1);
            if(val) printf("%s\n", val);
        }
        else 
        {
            printf("%s\n", _argv[1]);
        }
        return 1;
    }

    if(strcmp(_argv[0], "ls") == 0)
    {
        _argv[_argc++] = "--color";
        _argv[_argc] = NULL;
    }
    return 0;
}

int main()
{   
    while(!quit)
    {
        interact(commandline, sizeof(commandline));
        int argc = splitstring(commandline, argv);
        if(argc == 0) continue;

        int n = buildCommand(argv, argc);
        if(!n)
            NormalExcute(argv);
    }
    return 0;
}






























